The effect of the oral administration of various antigens on the ocular immune response has been tested in the animal model for severe intraocular inflammatory disease experimental autoimmune uveioretinitis induced by both retinal S-antigen and interphotoreceptor retinoid- binding protein (IRBP). Oral tolerance could be induced by repeatedly feeding rats S-antigen. A putative suppressor cell that was CD8 positive could be isolated from the spleen of such animals and transferred to other animals to induce a similar toleragenic effect. In addition, the role of the spleen was confirmed in ongoing animal experiments. A randomized masked trial to evaluate the usefulness of S-antigen feeding in patients with intraocular inflammatory diseases has been put together. A pilot study performed in two patients gave evidence of the induction of such tolerance.